Steam generating and resuperheating plant



Dec. 29, 1959 E. NICKEL 2,918,909

STEAM GENERATING AND RESUPERHEATING PLANT Filed Sept. 7, 1956 4 Sheets-Sheet 1 'Il I El 1- E |I||i $1 I INVENTOR. @A l BY Essen/a RD [We/r51.

ATTOR/VL'K Dec. 29, 1959 E. NICKEL STEAM GENERATING AND RESUPERHEATING PLANT 4 Sheets-Sheet 2 Filed Sept. 7, 1956 INVENTOR AMA/ W- 4 4. ATTORNEK 'IIIIA'IIIIII'II" IIIIIIIIIIIIIIIIIIIIII/l IIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIII/ IIIIIIIIIIIIA Dec. 29, 1959 E. NICKEL 2,918,909

STEAM GENERATING AND RESUPERHEATING PLANT Filed Sept. 7, 1956 4 Sheets-Sheet 3 IN V EN TOR.

EBEIPHARD MCKEL.

ATTORNEYS.

Dec. 29, 1959 E. NICKEL STEAM GENERATING AND RESUPERHEATING PLANT 4 Sheets-Sheet 4 Filed Sept. 7, 1956 kilb QUU b INVENTOR.

ESE/FHA [PD Mc/(EL,

ATTO/FNEK United States Patent STEAM- GENERATING AND RESUPERHEATING PLANT Eberhard Nickel, Stuttgart-Wangen, Germany, assignor to Sulzer Freres, S.A., Winterthur, Switzerland, a corporation of Switzerland Application September 7, 1956, Serial No. 608,456

Claims priority, application Germany September 9, 1955 3 Claims. (Cl. 1221) The present invention relates to a steam generating and resuperheating plant having a. plurality of individually fired combustion apparatuses, each apparatus including acombustion gas conduit in which tubular heat exchangers are placed. A heat exchanger for heating and evaporating the water or other suitable operating medium is placed in each gas conduit, these heat exchangers being arranged in parallel with respect to the flow of the operating medium therethrough.

The arrangement of steam superheaters and particularly of resuperheaters in plants of the aforedescribed type is difiicult because the steam to be resupcrheated must-be correctly distributed into tubular heat exchangers located in the several combustion gas conduits. Complicated control and regulating devices as well as expensive and space consuming conduits must be provided. The steam resuperheated in different combustion gas conduits must not only be collected into one conduit but must also be thoroughly mixed because the heating eflect of the difierent combustion apparatuses is not always thesame.

Thepresent invention overcomes this difficulty by conducting steam, which is to be superheated or resuperheated, in series relationthrough heat exchanger portions in different combustion apparatuses.

The superheat or resuperheat temperature can be controlled over a Wide range by suitable regulation of the heat supplied to the different combustion apparatuses.

In conventional multiple furnace boilers it is very difficult to obtain a high resuperheat temperature unless the resuperheaters are placed in the zones of veryhigh combustion gas temperatures. When starting a steam generator, there is usually no steam which must be resuperheated and there is no steam for cooling the resuperheater tube sections. The steam generator must therefore be heated very slowly to avoid excessive temperature of the resuperheater tube sections.

According to the invention one portion or heating stage of the resuperheater is placed in the combustion gas conduit of one combustion apparatus and another heating stage or portion of the same resuperheater is heater may be arranged in the same temperature zone of the respective'combustion gas ducts or they maybe located in ditterent temperature zones.

The individualportions of the superheater or of the resuperheater need not be of the same size. If the heating surface of one portion is greater than that of another portion the same amount of heat may be trans- "ice 2 ferred-to each-portion although the temperature 'of the steam entering the individual portions is different. With this construction thedesired reheat temperature can be maintained, also at partial loads although firing of any one of the combustion apparatuses may be interrupted to reduce steam output.

The combustion apparatus of the part of the steam generator in which a portion of the resuperheater is arranged in-a relatively low temperature zone can be rapidly heated up from cold without endangering the resuperheater. If the live steam produced in this part of the steam generator is expanded, for example in a steam turbine, and returned to the resuperheater, the latter is etfectively cooled so that also the other-part of the steam generator can be brought up to full load.

The invention is not limitedto the arrangement of one superheater or-resup'erheater whose sections are distributed over a plurality of steam generators. Several superheaters or resuperheaters may be so arranged.

It is of advantage to divide the superheater or resuperheater into a plurality of tube systems connected in parallel withrespect to the flow of the steam to be resuperheated, each system including a plurality of sections which are connected in series and located in difierent combustion gas conduits. The sections of the superheater or resuperheater may be arranged in the different combustion gas conduits in such a manner tha-t'the same pattern of sections belonging to diiferent systems is associated with each combustion apparatus.

By using a plurality of tube systems in parallel relation with respect to the flow of the steam and a plurality-of sections in series ineach system all sections may be constructed alike, reducing first cost. By interlacing the sections of difierent'tube systems in the individual combustion gas conduits control of the superheat or resuperheat temperature is facilitated over a wide range of load. If desired, the individual sectionsmay be syr'n-- metrically arranged in the different combustion gas conduits and located in the same temperature zones of the dilferent combustion gas conduits. The relative amounts of steam-flowing through difierentparallel tube systems are preferably "adjusted to be the same at all load conditions.

The novel featureswhich are considered characteristic of the invention are set forth with particularity in'the appended claims. The invention itself however and additional objects and advantages thereof will best be understood from the following description-of embodiments thereof when read in connection with-the accompanying drawing in which:

Figure 1 is a diagrammatic illustration of a steam generator and resuperheater according to the invention;

Figure '2 is a diagrammatic'illustration of a modifi'ed steam generator and resuperheater according to the invention;

Figure 3 is a diagrammatic illustration ofa third modification*'of a steam generator and'resuperheate'r according to the invention;

Figure 4 is a diagrammatic illustration of another modification of a steam generator and resuperheater according to theinvention;

Figure 5 is a diagrammatic illustration of --'a steam generator and resuperheater, in whichthe latter issplit into two systems arranged inparallel with respect to' the flow of ste'am'therethrough, each systemincluding a 5111- rality of'sect-ions arrangedin series rel-ation and located in different combustion Zgas conduits;

Figure 6 is a diagram'matic*illustration of a modified steam generator and resuperheater 'of the'typ'e shown in Figure 5;

Figures 7 and 8 illustrate two embodiments of the invention in which the live steam superheaters extend through a plurality of boiler units.

Like numerals designate like parts in different figures of the drawing.

Referring more particularly to Figure 1, numerals 1 and 2 designate steam generator portions having cornbustion chambers 3 and 4, respectively. The hot combustion gases flow from the combustion chambers 3 and 4 into combustion gas conduits or flues 5 and 6, respectively. Feed water is pumped by a pump 7 into tubular heat exchanger sections 11 and 11' located in the flues 5 and 6, respectively, and therefrom into tubes 12 and 12 lining the walls of the combustion chambers 3 and 4, respectively. After passing water separators 8 and 8 the operating medium flows in series through superheater sections 13, 14 and 13', 14', respectively. The live steam which has the desired temperature is conducted from the superheater sections 14 and 14' into a steam main 20 and therefrom through a high pressure turbine 17. The ex haust of the latter passes through a first resuperheater portion 15 located in the combustion gas conduit of the boiler part 2 and thereupon through a second resuperheater portion 16 located in the boiler part 1. The re superheated steam expands in a medium pressure turbine 18 and in a low pressure turbine 19.

Figure 2 shows a forced flow steam generator which is divided into two parts: A and B. The combustion chambers of these parts are lined with tubes 21 and 21, respectively, receiving hot water from tube sections 22 and 22, respectively, located in flues receiving hot combustion gases from the combustion chambers 3 and 4, respectively. The tube sections 22 and 22' are supplied with water by a feed pump 7.

The steam emerging from the tube sections 21 and 21 passes through water separators 8 and 8', respectively, and therefrom intO superheaters comprising consecutive sections 23, 24, 25, 26 and 23', 24, 25, 26, respectively. The superheated steam operates a high pressure turbine 17 from which it is returned to a first resuperheater section 27' in the boiler part B. A second resuperheater section 27 located in the boiler part A receives steam from the section 27 and delivers the resuperheated steam to a turbine 18.

An inspection of Figure 2 reveals that the combustion gases in the boiler section A pass consecutively over the superheater sections 23, 25 and the resuperheater section 27 and thereupon over the superheater sections 26 and 24, the latter receiving relatively cool gases.

In the boiler part B, the combustion gases pass through all superheater sections 23', 25', 26 and 24 before reaching the resuperheater section 27 which receives relatively cool gases. The boiler part B can therefore be rapidly heated from cold without damaging the resuperheater section 27. As soon as the turbine 17 is in operation, steam flows through the resuperheater sections 27' and 27, the latter being close to the combustion chamber of the boiler part A and receiving relatively hot gases. Boiler part A can now also be quickly brought up to full load operation.

Figure 3 relates to a twin boiler of the same structure as that shown in Figure 1 and description of the identical parts which are designated by the same numerals is not repeated. The steam produced in the boiler part 1 passes from the water separator 8 into a superheater having consecutive sections 28 and 29. The steam produced in boiler part 2 passes from the water separator 8 into a superheater having consecutive sections 28 and 29'. The steam from the superheater sections 29 and 29' passes through a high pressure turbine 17 and therefrom through a first resuperheater section 30 in the flue of the boiler part 2. Resuperheating is completed in a second resuperheater section 31 in the flue of the boiler part 1. Both resuperheater sections are located in flue gas zones of the boiler parts 1 and 2 in which the temperatures are substantially the same. The second section 31, however,

4 has a greater heating surface than the first section 30 so that about the same amount of heat is absorbed by each section although the steam temperature at the inlet of the section 31 is much higher than the temperature of the steam entering the first section 30.

Figure 4 illustrates an arrangement with two resuperheaters. The structure of the steam generating parts and of the flues of the parts 1 and 2 of the twin-boiler is substantially the same as that of the embodiments of the invention shown in Figures 1 and 3. The superheaters comprising consecuetive parts 32, 33 and 32, 33' Iv ceiving steam from the water separators 8 and 8, respectively, are located in relatively cool flue gas zones. The superheated steam operates the high pressure turbine 17 whose exhaust steam is resuperheated in a first resuperheater section 34 in the steam generator part 1 and thereupon in a second resuperheater section 34 in the boiler part 2.

The resuperheated steam drives a first medium pressure turbine 18 whose exhaust steam is resuperheated in a low pressure resuperheater section 35 in boiler part 1 and subsequently in a resuperheater section 35' in boiler part 2. The low pressure resuperheated steam drives a second medium pressure turbine 18' whose exhaust is conducted into a low pressure turbine 19.

Both resuperheaters are located in substantially the same flue gas temperature zones and it does not make any difference whether the combustion apparatus of boiler part 1 or 2 is shut down for reducing steam production.

In the modifications shown in Figures 2 to 4 the resuperheater heating surfaces are arranged in counterflow relation to the combustion gas. It is no departure from the present invention if the resuperheater heating surfaces are in parallel or transverse flow relation to the hot combustion gases or if the resuperheaters are used for absorbing radiant heat of combustion.

Figure 5 shows an arrangement having two steam generators 1 and 2. Each steam generator has a cornbustion chamber 3 and 4, respectively. Feed water is supplied by a pump 7 and conducted into combustion gas heated heaters 11 and 11', the hot water flowing into tube sections 12 and 12' lining the walls of the combustion chambers 3 and 4, respectively. Here the water is evaporated, the steam passing through water separators 8 and 8, respectively, and therefrom into superheaters 49 and 49', respectively. The superheated steam is conducted through a high pressure turbine 17 whose exhaust is divided at 41 to flow in parallel relation through two resuperheater tube systems. One of said systems includes a section 36 arranged in the combustion gas conduit of the generator 1, and a section 37 arranged in a different temperature zone of the combustion gas conduit of the steam generator 2, the sections 36 and 37 being connected in series with respect to the flow of steam therethrough. The other system includes a section 38 arranged in the combustion gas conduit of the generator 2 and a section 39 connected in series with section 38 and located in the combustion gas conduit of the generator 1, however, in a temperature zone which is diiferent from the zone in which the section 38 is located in the generator 2. The two systems are connected at 40 for supplying resuperheated steam to a medium pressure turbine 18. The exhaust of the latter is conducted into a low pressure turbine 19. The resuperheater sections 36 and 39 which belong to different tube systems are interposed in the hot gas stream between the combustion chamber 3 and the superheater 19. The resuperheater sections 37 and 38 which also belong to diflerent tube systems are interposed in the combustion gas stream between the combustion chamber 4 and the superheater 19.

In the modification shown in Figure 6 the arrangement of steam generators 1 and 2, of water heaters 11, 11', of evaporators 12, 12', of water separators 8, 8', and of superheaters 49, 49 is substantially the same as in Figure 5. -Thesteam'exhausting'from the high pressure turbine'17 is divided at-41 and conducted into 'two tube systems through which the steam flows in parallel relation. One tube system includes a first section 42 placed in the combustion gas conduit'ot the generator'l, a second section 43ilocated .in the combustion gas conduit of the generator 2, and a third section 44 placed in the combustion gas conduit of the generator 1. The other system includes a first section ,45 placed in the flue gas conduit of the generatorZ, asecond section 46 placed in the combustion. gas Conduit of the generator 1, and -a third section 47 located .in;the:combustion gasconduit of the generator 2. The reheated steam of the two systems is combined at 40 to drive the medium pressure turbine 18 which exhausts into a low pressure-turbine 19. The resuperheater sections 42, 46, 44 are substantially consecutively passed by hot combustion gases emerging from the combustion chamber 3, section 42 receiving the relatively hottest and section 44 the relatively coolest gases. In the steam generator 2 the hot combustion gases emerging from the combustion chamber 4 pass first over the resuperheater section 45, then over the section 43, and lastly over the section 47. The steam of each parallel tube system of the resuperheater thus passes first through a most heated section (42, 45), then through a medium heated section (43, 46), and thereupon through a section (44, 47) in a relatively low temperature gas zone. The heating effect on each tube system is therefore substantially the same. The arrangement of the superheaters and resuperheaters in the gas stream may, of course, be varied to suit individual requirements without departing from the scope of the invention;

Figure 7 illustrates an arrangement in which not only the resuperheaters but also the live steam superheaters extend through a plurality of boiler or heating units 50 and 51, each unit including a combustion chamber 3, 4, respectively, and a flue receiving combustion gas from the respective combustion chamber. The feed water is supplied by a feed pump 7 and divided into two streams, one passing through an economizer section 52 in the last flue of the boiler unit 50, the other stream passing through an economizer section 52' in the last flue of the boiler unit 51. The water, preheated in the sections 52 and 52, is forced through tube sections 53 and 53, respectively, lining the combustion chambers 3 and 4 of the boiler units 50 and 51, respectively, where the water is converted into steam. Water mixed with the steam leaving the sections 53 and 53' is separated in separators 8 and 8', respectively.

The steam separated in the separator 8 is conducted into a first superheater section 54 located in a relatively cold portion of the path of the combustion gases produced in the combustion chamber 3 and is then conducted into a second superheater section 55 which is located in a relatively hot part of the path of the combustion gases coming from the combustion chamber 4. The steam leaving the section 55 is conducted into a steam main 56.

The steam separated in the separator 8' is conducted into a first superheater section 57 located in a relatively cold zone of the flue gases coming from the combustion chamber 4. The steam leaving the section 57 is passed through a second superheater section 58 which is located in a relatively hot zone of the combustion gases coming from the combustion chamber 3' and is thereupon also conducted into the steam main 56.

The thus produced live steam operates a high pressure turbine 17 forming part of a turbine unit including two medium pressure turbines 18 and 18', and a low pressure turbine 19, the turbine unit driving an electric generator 59.

The exhaust steam of the turbine 17 is passed through a first resuperheater section 60 heated by hot combustion gases emerging from the combustion chamber .3 and is thereupon passed through=a secon'd resuperheater sectiori -61-heate'd'by hot combustion'gases emerging from'thc turbine 19.

' The plant shown in Figure 8 is similar to that shownin Figure 7 as far as the steam'generating partup'to the separators 8 and 8' is concerned. The live steam superheaters and the resuperheaters, however, are arranged in different flue gas temperature zones.

The steam leaving the separator 8 is passed through a first superheater section 64 which is placed directly at the gas outlet of the combustion chamber 3. The steam leaving the section 64 is conducted through a second superheater section 65 which is located in a relatively cold zone of the combustion gases leaving the combustion chamber 4. The steam superheated in the sections 64 and 65 is conducted into a steam main 56.

The steam leaving the separator 8 is passed through a first superheater section 66 located directly at the gas outlet of the combustion chamber 4. From the section 66 the steam is conducted into a second superheater section 67 located in a relatively cool zone of the gas stream emanating from the combustion chamber 3. The steam leaving the section 67 is conducted into the steam main 56 which is connected with the inlet of a high pressure turbine 17 The exhaust of the high pressure turbine 17 is conducted through a first resuperheater section 68 which receives hot combustion gases from the combustion chamber 4. From the first resuperheater section 68 the steam is conducted into a second resuperheater section 69 which is heated by hot gases from the combustion chamber 3 and discharges resuperheated steam into a medium pressure turbine 18. The latter exhausts into a low pressure turbine 19.

The turbines 17, 18, and 19 have a common shaft for driving an electric generator 59.

The individual boiler parts may be arranged in spaced relation or in blocks, as shown. The individual boiler parts are interconnected by the superheater or resuperheater sections which are connected in series and located in different boiler parts. Arrangement and control of the combustion gas ducts are individual for each boiler part.

The arrangements according to the invention afford a very good control of the superheat or resuperheat temperatures. However, conventional expedients for controlling superheat and resuperheat temperatures, such as swinging burners, recirculation of combustion gases, steam heated supplemental resuperheaters, and others may be combined with the arrangements according to the invention for making the control of the resuperheat temperature still more accurate.

What is claimed is:

1. A steam generating and superheating plant comprising a plurality of heating units, each of said heating units including a combustion chamber and a flue connected to said chamber for receiving combustion gas therefrom, feed water supply means, a tube system located in each of said units and being connected with said supply means for receiving feed Water therefrom and for con-' ducting the water in parallel relation through said units for heating and evaporating the water, a first superheater connected to one of said tube systems for receiving all of its steam therefrom, said first superheater having a first portion located in one of said units to be heated therein,

:7 said first superheater having a second portion located in a second of said units, said two portions being connected in series relation, a second superheater connected to a second of said tube systems for receiving all of its steam therefrom, said second superheater having a first portion located in the second of said units in which the second portion of said first superheater is located, said second superheater having a second portion connected in series relation to the first portion of said second superheater and located in the first unit in which said first portion of said first superheater is located.

2. A steam generating and superheating plant as defined in claim 1 including a resuperheater having a first portion located in one of said units and having a second portion located in a second of said units.

3. A steam generating and superheating plant accordin to claim 2 in which said resupcrheater portions are connected in series relation.

References Cited in the file of this patent UNITED STATES PATENTS 

